Oxidation behavior and thermal-shock resistance of AO20/Si3N4 coating for carbon/carbon composites

Abstract

A new Si3N4 coating was proposed and prepared as bonding layer for improving the high temperature thermal shock resistance of carbon/carbon composites (C/C). It is found that the mass loss of the AO20/Si3N4 coating was 0.60% after oxidation at 1723 K for 69 h in air, and 2.86% after oxidation at 1673 K for 134 h. In particular, the coating sample has excellent thermal shock resistance, where the mass loss of the sample is only 0.03% after 33 times of thermal shock from 1673 K to room temperature. The excellent oxidation and thermal shock resistance are mainly attributed to the better thermal expansion mismatch of the coatings, self-healing ability of the glass layer, and the formation of Si2N2O, which expected to enhance the potential application of C/C in more severe thermal shock environment.